\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\setCJKmainfont{Noto Serif CJK SC}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usepackage{wasysym}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes,}
\begin{document}
\small
\begin{tikzpicture}[>=latex,scale=1.7]
  % \useasboundingbox(0.9,0)rectangle(5.1,5);
  \draw[->] (0,-0.8)--(0,1.0)node [right]{$i$};
  \draw [->](-0.7,0)--(7,0)node [right]{$t$};
  \node at (0,0)[below left]{$O$};
  \draw [very thick] plot [domain=0:2*pi, samples=1000] function{0.6*sin(x)} ;
  \draw [very thick] plot [domain=0:2*pi, samples=1000] function{0.6*sin(pi*2/3+x)};
  \draw [very thick] plot [domain=0:2*pi, samples=1000] function{0.6*sin(pi*4/3+x)};
  \node at (pi/2, 0.9){$i_{AX}$};
  \node at (pi/2+pi*2/3, 0.9){$i_{BY}$};
  \node at (pi/2+pi*4/3, 0.9){$i_{CZ}$};
\draw[dashed] (pi*2/3, -0.8)--(pi*2/3, 1);
\draw[dashed] (pi*4/3, -0.8)--(pi*4/3, 1);
\draw[dashed] (pi*6/3, -0.8)--(pi*6/3, 1);
\node at  (pi*2/3+.2, 0)[below]{$\frac{1}{3}T$};
\node at  (pi*4/3+.2, 0)[below]{$\frac{2}{3}T$};
\node at (pi*6/3+.2, 0)[below]{$T$};
\end{tikzpicture}
\end{document}